Fast Idle occurs right after starting up a cold engine which lowers itself shortly after, once the car reaches its drivability.
- Idling refers to running a vehicle's engine when the vehicle is not in motion. This commonly occurs when drivers stopped at a red light, waiting while parked outside or otherwise stationary when the engine is running
- Idle speed is the rotational speed an engine runs when the engine is idling, that is when the engine is uncoupled from the drivetrain and the throttle pedal is not depressed. In combustion engines, idle speed is generally measured in revolutions per minute of the crankshaft